This invention relates to a tracer control method and, more particularly, to a tracer control method in a master-slave type tracer system provided with two tracer units, wherein a tracer head is made to trace a model on a first tracer unit side, the first tracer unit generates a move command for a second tracer unit side on the basis of the aforementioned tracing, and machining is performed on the second tracer unit side on the basis of the move command.
A master-slave type tracer system has at least two tracer units. A model is traced on the first tracer unit side (master side), the first tracer unit generates a move command for a second tracer unit side (slave side) on the basis of the aforementioned tracing, and machining is performed on the slave side on the basis of the move command. The individual tracer units constituting such a master-slave type tracer system operate by causing a tracer head to trace a model, calculating velocity commands along various axes by means of a tracer control circuit using a deflection quantity sensed by the tracer head, driving motors for the corresponding axes on the basis of the analog velocity commands to transport a tool relative to a workpiece, and repeating these operations to machine the workpiece into a shape identical with that of the model. To carry out master-slave tracer control, the arrangement is such that an analog velocity command voltage produced as an output by the tracer control circuit of one tracer unit (master side) is applied to a velocity control unit of the other tracer unit (slave side) through an analog gate.
Thus, in the conventional master-slave system, a velocity command is produced in the form of an analog value, and the move command transmitted from the master side to the slave side also is an analog value. Consequently, the system is susceptible to disturbance such as supply voltage fluctuation or noise, so that accurate commands cannot be generated. The disadvantageous result is that highly precise tracer machining cannot be performed.
Further, since the move command sent from the master side to the slave side is applied as an analog velocity command in the above-described master-slave system, a drawback is that the machined profile cannot be enlarged or reduced in size with respect to the model profile.